Streamline Your API Testing with Jest and Cucumber: A Powerful BDD Approach

In today’s API-driven world, ensuring the reliability and functionality of your APIs is crucial. Manual testing can be time-consuming and error-prone, making automation essential. This is where Jest and Cucumber come in, offering a powerful combination for Behavior-Driven Development (BDD) in API automation testing.

What is Jest? 

Jest is a popular JavaScript testing framework known for its ease of use, rich features, and seamless integration with various tools. It provides a robust testing environment with features like:

• Expect assertions:Jest offers a variety of assertion methods to validate test outcomes.
• Test runners:Jest includes a built-in test runner that executes tests and provides detailed reports.
• Mocking:Jest allows you to mock external dependencies for isolated unit testing.

What is Cucumber? 

Cucumber is a BDD framework that promotes collaboration between developers, testers, and stakeholders. It uses a human-readable Gherkin syntax to define test scenarios in plain English. This fosters clear communication and a shared understanding of API behaviour.

Why Jest and Cucumber Together? 

By combining Jest’s powerful testing capabilities with Cucumber’s BDD approach, you can achieve several benefits: 

• Improved Readability: Gherkin syntax makes tests easier to understand for both technical and non-technical audiences.
• Enhanced Maintainability:BDD-style tests are more maintainable as they focus on API behaviour rather than implementation details.
• Increased Collaboration:Clear test scenarios in plain English promote collaboration between teams.
• Faster Feedback:Jest’s efficient test execution facilitates rapid feedback cycles.

Getting Started with Jest and Cucumber

Here’s a basic overview of setting up Jest and Cucumber for API automation testing:

api-tests/
|— node_modules

|— src/
|     |— features
|             |— steps
|             |     |— getTodos.steps.ts
|             |— getTodos.feature
|— babel.config.js
|— tsconfig.json
|— package.json

1. Project Setup: Initialize a Node.js project with typescript enabled and install Jest, Cucumber, and a testing library like axios or node fetch for making HTTP requests.
2. Feature Files:Create .feature files to define API behaviour using Gherkin syntax. These files will outline scenarios with Given, When, Then steps.
3. Step Definitions:Implement step definitions in JavaScript/typescript to map Gherkin steps to actual API calls and assertions using Jest’s “expect” methods.
4. Test Execution:Run Jest to execute the tests defined in your feature files and step definitions.

Example Feature File

Consider a simple API for fetching Todos information. Here’s an example feature file outlining a scenario for retrieving a Todo:

Feature: Todo features
Scenario: Get the todo’s
Given I have the base_url
When I send get request
Then I should get 200 response

Example Steps File

import { loadFeature, defineFeature } from ‘jest-cucumber’; import axios, { AxiosResponse } from ‘axios’;
const feature = loadFeature(<path_for_the_feature_file>);
defineFeature(feature, (test) => {
test(“Get the todo’s” ({ given, when, then }) => {
>
let response:AxiosResponse;
let base_url:string;
given(‘I have the base_url’, async () => {
base_url=””;
});
when(‘I send get request’,async () => { response-await
axios.get(“https://jsonplaceholder.typicode.com/todos”);
});
then(‘I should get 200 response’, () => {
expect(response.status).toBe (200);
});
});
}); 

Benefits of Jest and Cucumber for API Automation 

• Increased Test Coverage: BDD encourages writing tests for various API functionalities, leading to comprehensive test coverage.
• Reduced Maintenance: Focus on behaviour makes tests less susceptible to code changes.
• Improved Developer Experience: BDD fosters communication and collaboration, leading to a better developer experience.

About Author

Debashis Badajena is a skilled software engineer excelling in MERN stack, E2E testing, unit testing, and API testing. Focused on React, good at making websites easy to use and fast. Armed with expertise in JavaScript and TypeScript, he is eager to take on new challenges and drive innovation in the dynamic world of technology.